When you freeze a chunk of sapphire coated in yttrium barium copper oxide, what do you get? A puck that can whiz around a magnetic track like a hovercraft. When the oxide gets very cold, it becomes a superconductor and actively repels magnets, with the result that when it’s placed over a large enough magnet, it levitates.

As the Tel Aviv University team behind this video explains, despite the puck’s aversion to magnetic fields, the thinness of the oxide layer on it means that the field does manage to penetrate it a little. But only in tiny columns called flux tubes. The puck doesn’t like having those flux tubes moved around in it, which happens whenever it moves. And in order to minimize the shifting of the flux tubes, it…floats. It’s a phenomenon called quantum locking.

How essential is the sapphire? Could the oxide coating be applied to other materials instead and still exhibit this behaviour?

Chris

That is so cool (pun intended)!

eyesoars

The sapphire is not essential. The thin layer of YBCO, however, allows flux lines to penetrate, where a solid puck of superconductor would probably not.

What is essential is that this is a type II superconductor (which allows magnetic flux penetration, and (just for practicality’s sake), allows the use of liquid nitrogen), and that the magnetic flux actually can and does penetrate.

Could this be used for armor on a space craft that can be easily be moved around the exterior of the craft? For example armor sections could be moved to intercept space debris or be moved to cover a hole punched by the debris. What am I missing that would make this impractical?